1. Field of the Invention
The present invention is related to a manufacturing method of an organic electroluminescent device using electroluminescent phenomena of organic thin film and an organic electroluminescent device.
2. Description of the Related Art
Organic electroluminescent device is explained below.
Organic electroluminescent device includes organic a luminous layer of electroconductivity and a transparent electrode layer and a counter electrode layer which are placed on either side of this organic luminous layer. As for the organic electroluminescent device, transparent electrode layer, organic luminous layer and counter electrode layer are laminated on a substrate of translucency by this sequence.
And, by means of applying voltage to organic luminous layer, electron and hole are poured into organic luminous layer. Then electron and hole couple again. Organic luminous layer emits light in this coupling.
A hole transport layer may be provided between the transparent electrode layer and the organic luminous layer which are anode to improve luminous efficiency of organic luminous layer. The electron transport layer may be provided between the counter electrode layer that is cathode and the organic luminous layer.
Generally, as for the organic luminous layer, the hole transport layer and the electron transport layer, molecular weight is high. Therefore, these layers are formed by functional material comprising polymeric materials which are easy to be dissolved in solvent. Thus, wet coating method such as spin coat method in air pressure and printing methods such as relief printing, inversion offset printing (for example, Japanese Patent Laid-Open No. 2003-17248 Official Gazette) or ink jet printing method (for example, The 3,541,625th Patent Official Gazette) are used, and each layer can be formed. Therefore, reduction of a cost of production facility and improvement of productivity can be planned.
However, in the above described manufacturing method of conventional organic electroluminescent device, there is the following problem:
When there is unevenness in the surface of transparent electrode layer, this unevenness cannot be coated uniformly. This problem is based on grounds of the following:
Organic luminous layer, hole transport layer and electron transport layer are formed respectively by using solution of functional material comprising polymeric materials. As density of this solution rises, viscosity of solution rises. Solution is printed on the surface of object by a printing method. However, till this solution dries, unevenness in the surface of object cannot be coated. Thus, because a high electric field is applied to the point where film thickness of organic luminous layer is thin locally, the point is subjected to big load. Therefore extra, flattening the surface of electrode layer is necessary. By way of example only, after having formed transparent electrode layer on a substrate, surface of the transparent electrode layer is polished.
The present invention was made in view of the above-mentioned problem. The present invention is aimed at providing a manufacturing method of organic electroluminescent device and the organic electroluminescent device that this unevenness is covered by the organic luminescence media layer without being affected by unevenness in the surface of the transparent electrode layer.